The present invention relates to an oil pump and, particularly to an internal gear type oil pump which serves as a lubricating pump for a vehicle engine.
One of previously known oil pumps of this type is disclosed, for example, in JP-U 61-171885. This oil pump comprises an external tooth type drive gear or inner gear which is connected to a drive shaft such as a crankshaft for unitary rotation therewith, and a driven gear or outer gear which has internal teeth engaged with external teeth of the inner gear and is received in a space or pump chamber of a pump housing in a manner to be nonconcentric with the inner gear for rotating therewith. Oil is delivered to an engine, and so forth, due to volume variations of a cavity defined between addendums of the two gears when the drive shaft rotates. Additionally, the inner gear has a collar portion for positioning in the pump housing.
With the previously known oil pump, the collar portion of the inner gear permits positioning of the inner gear. However, since the collar portion protrudes from the inner gear in an axial direction thereof, the oil pump has an increased overall length in the axial direction, and machining of the inner gear itself is complicated, resulting in an increase in its manufacturing cost.
It is, therefore, an object of the present invention to provide an oil pump which has a decreased overall length in an axial direction thereof, with simple machining and easy positioning of an inner gear upon mounting.